Arthroscopic shaver

ABSTRACT

An improved surgical device and method for manufacturing the device are provided. The device is a high rotating speed arthroscopic probe shaver with bearing means that give superior longitudinal and radial support. Further, the outer tube of the probe shave is swaged to fit very closely over the inner tube.

FIELD OF THE INVENTION

The present invention relates to surgical tools for cutting and removingtissue from the body. In particular, the present invention is useful forperforming intra-articular surgery through arthroscopy withoutunnecessary surgery on the joint.

BACKGROUND OF THE INVENTION

Arthroscopy is becoming a popular method for removing diseased ordamaged tissue from intra-articular regions of the body. Basically,arthroscopy is a method of surgery involving the use of probes forviewing and operating on regions of the body such as knee joints andother intra-articular regions. Its benefits arise from the smallerincisions involved which cause less scarring and heal more quickly thanlarger incisions required for other surgical techniques.

A variety of cutting devices have been developed for arthroscopy whichinclude an outer tube sized and shaped for insertion through a puncturein the flesh with an inner tube adapted to rotate relative to the outertube. These cutting devices typically have a side-facing opening throughthe inner and outer tubes into which tissue is drawn by a partial vacuumin the inner tube. As the inner tube rotates relative to the outer tube,the tissue drawn into the opening by the vacuum is cut off by thecutting interaction of the edges along the openings or of bladesotherwise located in the instrument. This type of device is showngenerally in U.S. Pat. Nos. 4,210,146; 4,203,444; 4,167,944; 3,996,935;3,945,375; 3,844,272; and 3,618,611.

As surgeons gained greater experience with these devices, it becameapparent that they operated better at higher rotating speeds. It wasfound that tissues tended to be cut in smaller pieces and less tearingof the tissues occurred at higher RPM's. At these higher operationalspeeds, bearings or other means for maintaining the alignment of theinner cutting member relative to the outer tube became increasingly moreimportant.

Attempts to develop devices with improved alignment are described inseveral U.S. patents. For example, U.S. Pat. No. 4,203,444 shows radialbearing surfaces 33, 35 on each side of the cutting blade at theside-facing window at FIG. 4 and a ring 37 at FIG. 3 for journaling theinner tube within the outer tube. U.S. Pat. No. 3,996,935 shows aconical inner seat 75 at the end of the outer tube with the tip of theconical seat pointing outwardly at the axial centerline of the tube anda corresponding end portion on the inner cutting member with a conicalexterior surface 78 at FIG. 7. U.S. Pat. No. 3,844,272, by the sameinventor as U.S. Pat. No. 3,996,935, shows a similar conical seatarrangement at FIG. 18A. This arrangement requires that the cuttingopening be located at a relatively great distance from the tip becauseof the length of the solid bar necessary to form the bearing, causingunnecessary tissue disturbance.

None of these devices is believed to have a satisfactory bearingarrangement for maintaining proper axial alignment during operations athigher speeds and under non-axial loading conditions.

SUMMARY OF THE INVENTION

The present invention is directed to an improved bearing arrangementwhich is useful for extending the life and dependability of a poweredarthroscopic probe shaver of the type that includes an outer tube and aninner tube that rotates at relatively high speeds to cause shavingaction along the edges of a side-facing opening near the distal end ofthe probe. The bearing includes a first bearing surface which extendsinwardly from the distal end of the outer tube and a secondcomplementary bearing surface on the distal end of the inner tube whichoverlaps and cooperates with the first bearing surface in an annularspace between the first bearing surface and the inner side surface ofthe outer tube. It is found that this type of bearing configurationmaintains the alignment of the inner and outer tubes in a manner thatprovides both radial and longitudinal thrust bearing support andsignificantly reduces wear between the inner side surface of the outertube and the outer side surface of the inner tube. This relationshipplaces the cutting opening closer to the distal end of the instrumentthan possible for other configurations and tends to minimize tissuedisturbance during surgery.

The alignment of the inner and outer tubes can be further maintained byswaging the outer tube to fit closely over an inner tube which has asmooth outer surface.

BRIEF DESCRIPTION OF THE DRAWINGS

For a better understanding of the invention, reference may be had to thefollowing description of an exemplary embodiment of the invention takenin conjunction with the accompanying drawings in which:

FIG. 1 is a perspective view of the improved arthroscopic probe shavershowing the inner tube withdrawn from the outer tube;

FIG. 2 is a side elevational view of the improved arthroscopic probeshaver with a cutaway showing the inner tube;

FIG. 3 is a top view of the distal end of the improved arthroscopicprobe shaver;

FIG. 4 is a sectional view taken along the line 4--4 of FIG. 2;

FIG. 5 is a sectional view showing the side-facing opening taken alongthe line 5--5 in FIG. 2;

FIG. 6 is a side-sectional view of the distal end of the arthroscopicprobe cutter showing the inner tube fully engaged with the outer tube;and

FIG. 7 is a side-sectional view of the distal end of the inner tube withthe distal end of the outer tube shown removed longitudinally.

DETAILED DESCRIPTION OF THE EMBODIMENT

An exemplary embodiment of the improved arthroscopic probe cutter of thepresent invention is described with reference to the drawings along withan improved method for manufacturing the probe. The improvedarthroscopic probe cutter will be referred to in this specificationgenerally by reference letter P.

As can be seen from the drawings, the probe P is elongate and otherwisesized and shaped for insertion through a puncture in the flesh of abody. The probe P is made up of an inner tube I and an outer tube T. Theoutside diameter of the inner tube I, which defines an outer sidesurface 20 of the inner tube I, is substantially equal to but slightlysmaller than the inside diameter of the outer tube T which defines aninner side surface 18 of the outer tube T.

As shown in FIG. 4, the inner tube I fits into the outer tube T and theinner side surface 18 of the outer tube T is close to the outer sidesurface 20 of the inner tube T. The outer side surface 20 of the innertube I and the inner side surface 18 of the outer tube T both havesmooth finishes to reduce friction and allow the inner tube I to rotaterelative to the outer tube T.

The probe P has proximal and distal ends which are generally designatedas reference numerals 12, 15, respectively. The proximal end 12 isadapted for connection to a motor or other type of driving mechanism(not shown), through a proximal seat 14 formed on the outer tube T and aproximal connection 13 formed on the inner tube I. The connections 13,14 are shaped so that they can engage the driver which operates to holdthe outer tube T stationary while rotating the inner tube I to performthe arthroscopic operation. The configurations of the connectors 13, 14are merely illustrative and others can be used to adapt the invention todifferent types of driving mechanisms.

As shown in FIG. 1, both the inner tube I and the outer tube T haveside-facing openings S near the distal end 15 of the probe P. Theside-facing openings S co-act in a cutting or shaving action asdescribed in greater detail below. The shaver operates to draw tissue(not shown) into the side-facing openings by creating a suction in theinner tube I in a conventional manner. Tissue sucked into the opening Sis then cut in a compound scissor fashion as the inner tube I rotatesrelative to the outer tube T. The suction then draws the tissue shavingsaway from the distal end 15 of the probe P to avoid clogging of theopening S.

The side-facing opening S of the inner tube I is defined by a blade edge10 and the opening of the outer tube T by a cooperating edge 11 whichco-acts with the blade edge 10. As the inner tube I rotates, the bladeedge 10 on the inner tube I moves past the cooperating edge 11 and thecooperating oval shaped openings slice the tissue at two points until itis completely cut off at the respective centers of the openings as theypass each other.

As shown in FIG. 5, the blade edge 10 of the inner tube I is formed witha blade surface 24 which is preferably formed at an angle to thevertical sufficient to form a sharp cutting edge. The cooperating edge11 of the outer tube T is formed on a rim surface 23 which issubstantially perpendicular to the inner side surface 18 of the outertube T. Further, the openings are formed so that the blade edges 10, 11are elliptical in shape (see FIG. 3) with the widest part of the openingslightly above the centerline of the probe as shown in FIG. 5. As theinner tube I rotates and closes the ellipse of the stationary outer tubeT, the elliptical or oval shape ensures that the cutting or shavingaction will proceed longitudinally from the ends of the opening S towardthe center. With oval or elliptical openings S, the highest cuttingstress occurs at the center of the openings S rather than nearer thedistal end 15 of the probe P as with openings of different shapes. Ithas been found that oval openings S provide a shaving or cutting actionthat is less prone to clogging of the opening. Openings of this shapealso tend to minimize stresses in the tip of the cutting instrument.

As can be seen in FIGS. 6 and 7, the invention includes a unique bearingarrangement designated generally by the reference letter B at the distalend 15 of the probe P for supporting and aligning the inner tube Irelative to the outer tube T. The bearing B includes a first bearingsurface 16 which projects into the outer tube T and forms an annularspace 17 (see FIG. 7) between the first bearing surface 16 and the innerside surface 18 of the outer tube T. A second bearing surface 19 isformed on the distal end 15 of the inner tube I, which is adapted tooverlap and cooperate with the first bearing surface 16 in the annularspace 17. The bearing B provides both radial and longitudinal thrustbearing support and maintains the alignment of the inner tube I relativeto the outer tube T.

As shown in FIGS. 6 and 7, the first bearing surface 16 is formed on theouter conical surface of a truncated cone which projects into the distalend 15 of the outer tube T. The second bearing surface 19 is formed as abeveled surface which defines an opening 21 on the distal end 15 of theinner tube I, this surface overlapping and cooperating with the outerconical surface of the first bearing surface 16.

The first bearing surface 16 is formed on a plug 22 that is adapted tofit in the distal end 15 of the outer tube T which is open. The plug 22is formed so that the inner end 26 defines a truncated cone with theouter conical surface defining the first bearing surface 16. The plug 22is fitted into the distal end 15 of the outer tube T and connected tothe outer tube T by brazing, welding, gluing, or other means known inthe art.

An additional feature of the present invention which provides furthersupport and alignment for the inner tube I relative to the outer tube Tis that the outer tube T is swaged to fit closely over the inner tube I.It is found that a swaged outer tube T provides a superior fit for theinner tube I and outer tube T of the probe P and helps eliminate radialwear. Further, the outer side surface 20 of the inner tube I is polishedto a smooth finish to reduce frictional drag between the tubes as theyrotate.

The improved arthroscopic probe cutter of the present invention can bemanufactured of any suitable non-corrosive material, but is preferablymade of #303 or #304 stainless steel. In order to obtain the superiorresults as taught by the present invention, the probe P can be assembledaccording to the method described below.

The probe P is formed so that the inner side surface 18 of the outertube T and the outer side surface 20 of the inner tube I are relativelysmooth. This can be accomplished by polishing the outer surface of theinner tube to at least a 32 micro finish at some stage in themanufacturing process. The inner surface of the outer tube is normallysmooth enough that it does not require additional treatment.

After the bearing assembly is formed and assembled as described above,the inner tube I is inserted into the outer tube T and the first bearingsurface 16 is brought into contact with the second bearing surface 19.The probe P is then swaged to reduce the diameter of the outer tube andcause inner side surface 18 of the outer tube T to fit closely over theouter side surface 20 of the inner tube I. This is accomplished by usinga swaging tool to apply pressure on the outer surface of the outer tubeT. The fit should be tight enough to prevent undue play between thetubes, but loose enough to allow the inner tube I to rotate freely.

After the swaging step, the side-facing openings S are formedsimultaneously by cutting them while the inner tube I is inserted intothe outer tube T and the bearing means are engaged to assure that theopenings S coincide. The openings can be machined by means well known inthe art to form a rim surface 23 on the outer tube T that is generallyperpendicular to inner side surface 18 of the outer tube T. The surfacedefining the opening of the inner tube I is beveled to form a cuttingblade 24 as described above.

It will be appreciated that the improved arthroscopic probe shaver ofthe present invention will operate at rotating speeds of approximately200 RPM or higher with considerably more reliability and less wear onthe bearing surfaces than possible in the prior art. The location ofbearing surfaces in the distal end of the probe with the configurationdescribed above is believed to achieve superior results over those ofthe prior art. By swaging the outer tube and providing the close fitalong the length of the tubes, an accurate axial alignment is providedwhich results in greater precision during the surgical procedure.

The foregoing disclosure and description of the invention areillustrative and explanatory, and various changes in the size, shape andmaterials, as well as in the details of the illustrated construction maybe made without departing from the spirit of the invention.

I claim:
 1. A surgical instrument for cutting tissue, the instrumentcomprising:an outer tube sized and shaped for insertion through apuncture in the flesh of a body, the outer tube having a side-facingopening therein for the entrance of tissue to be cut; an inner tubefitted in the outer tube and adapted to rotate relative to the outertube, the inner tube including a side-facing opening defining a bladeadapted to co-act in cutting action with a cooperating edge of theside-facing opening of the outer tube; the inner tube further includinga longitudinal opening on its proximal end adapted for connection to asuction device for drawing fluid and cuttings into the openings and fordrawing the fluid and cuttings through the instrument; means forconnecting the inner tube to a drive motor for continuously rotating theinner tube relative to the outer tube so that the blade on the innertube is moved past the cooperating edge of the side-facing opening inthe outer tube; bearing means at the distal end of the inner and outertubes for supporting and aligning the inner tube relative to the outertube; the bearing means including a first bearing surface projectinginto the outer tube and forming an annular space that tapers inwardlyaway from the inner side surface of the outer tube; and a second bearingsurface at the distal end of the inner tube shaped and dimensioned tooverlap and cooperate with the first bearing surface and extend aroundsubstantially the entire distal end of the inner tube.
 2. Theimprovement of claim 1, wherein:the first bearing surface is formed onthe outer conical surface of a truncated cone projecting into the distalend of the outer tube; and the second bearing surface is beveled tooverlap and cooperate with the outer conical surface of the firstbearing surface.
 3. The improvement of claim 1, wherein:the outer tubeis swaged to fit closely over the inner tube; and the outer side surfaceof the inner tube is polished to a smooth finish.
 4. The improvement ofclaim 1, wherein:the outer tube is open at the distal end and the firstbearing surface is formed on a plug connected to the distal end of theouter tube.
 5. The improvement of claim 1, wherein the side-facingopenings in the inner and outer tubes are oval in shape.
 6. Theimprovement of claim 5, wherein the opening of the outer tube is formedentirely above the axial centerline of the tube and a rim surfacedefining the opening is substantially perpendicular to the inner sidesurface of the outer tube.
 7. The improvement of claim 6, wherein theblade edge of the opening of the inner tube is coincidental with thecooperating edge of the rim surface in the outer tube, and the bladedefining the opening of the inner tube is beveled.
 8. A surgicalinstrument for cutting tissue, the instrument comprising:an outer tubesized and shaped for insertion through a puncture in the flesh of abody, the outer tube having a side-facing opening therein for theentrance of tissue to be cut; an inner tube fitted in the outer tube andadapted to rotate relative to the outer tube, the inner tube including aside-facing opening defining a blade adapted to co-act in cutting actionwith a cooperating edge of the side-facing opening of the outer tube;the inner tube further including a longitudinal opening on its proximalend adapted for connection to a suction device for drawing fluid andcuttings into the openings and for drawing the fluid and cuttingsthrough the instrument; means for connecting the inner tube to a drivemotor for continuously rotating the inner tube relative to the outertube so that the blade on the inner tube is moved past the cooperatingedge of the side-facing opening in the outer tube; the outer tube havinga distal end portion, the outer tube opening being generally ellipticaland located within the distal end portion; the inner tube having adistal end portion, the inner tube opening being generally ellipticaland located within the distal end portion, the outer surface of theinner tub defining said inner tube opening being the same size and shapeas the inner surface of the outer tube defining said outer tube openingfor forming cooperating cutting surfaces for cutting tissue when theinner tube rotates relative to the outer tube.
 9. The improvement ofclaim 8, wherein the inner tube opening is beveled for forming a sharpcutting edge around the outer surface of the inner tube, which definessaid inner tube opening.
 10. The improvement of claim 8, and furtherincluding bearing means at the distal end of the inner and outer tubesfor supporting and aligning the inner tube relative to the outer tube,the bearing means including a first bearing surface projecting into theouter tube and forming an annular space between the first bearingsurface and the inner side surface of the outer tube, and a secondbearing surface at the distal end of the inner tube adapted to overlapand cooperate with the first bearing surface.